The Gunners have been linked with a £10 million bid for Atletico Madrid striker Adrian Lopez, while Crystal Palace's 21-year-old England international Wilfried Zaha and Schalke midfielder Lewis Holtby are others allegedly on Wenger's radar.
"It is very difficult because the level of expectation is very high - people want to see Lionel Messi come in, they don't want to see a promising guy," said Wenger, who takes his side to Swansea in the FA Cup third-round on Sunday.
He added: "First of all the name gives hope. When a guy has no name people are already sceptical, so it's much more difficult for us."
Swansea look to have picked up a real bargain in Michu, signed by manager Michael Laudrup for just £2 million from Rayo Vallecano, and the Spanish striker scored both goals in the 2-0 win at Arsenal on December 1.
Wenger admitted the 26-year-old had not been high on the watchlist of the Arsenal scouting network, which is now under more scrutiny than ever to unearth talent who can hit the ground running.
"Sometimes when you are on a big club your scouts are a bit more cautious because they think 'oh, it is Arsenal it has to be a top four player', so naturally they are looking less at players who play at smaller clubs," Wenger continued.
"You are always scared that he is a player who does not do well, the scouts are looked at as responsible. The competition is higher on scouting front, that is for sure.
"The country where we were really, really competitive was France, but now they produce less players than they did 10 or 15 years ago at the top, top level.
- Sports & Recreation
- Lionel Messi
- Adrian Lopez
- Lewis Holtby
- Wilfried Zaha